Synthesis and characterization of novel thermo-responsive F68 block copolymers with cell-adhesive RGD peptide

Thermoresponsive and injectable hydrogels consisting of F68, biodegradable oligomers, 4-META and RGD peptide were successfully synthesized. These modified F68 triblock copolymers consist of the PPO blocks core and the PEO blocks shell in aqueous solution. The alterations of hydrophobic interaction and chain mobility lead to the phase transition with increasing temperature. [Display omitted] ► Thermoresponsive and Injectable hydrogels consisting of F68, biodegradable oligomers, 4-META and RGD peptide were successfully synthesized. ► These modified F68 triblock copolymers consist of the PPO blocks core and the PEO blocks shell in aqueous solution. ► The alterations of hydrophobic interaction and chain mobility lead to the phase transition with increasing temperature. ► These hydrogel are anticipated to apply drug delivery and tissue engineering. Thermosensitive poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer, Pluronic F68, containing a hydrophobic unit, oligo-(lactic acid)(oligo-LA) or oligo-caprolactone (oligo-CL), 2-META and RGD as side groups was successfully synthesized and characterized by 1H NMR, FTIR, and elemental analysis. Their aqueous solution displayed special gel–sol–gel phase transition behavior with increasing temperature from 10 to 70°C, when the polymer concentration was above critical micelle concentration (CMC). The gel–sol phase diagram was investigated using tube inversion method, rheological measurement, and dynamic light scattering. Based on these results, the gelation properties of modified F68 were affected by several factors such as the composition of the substituents, chain length of oligo l-LA or oligo ε-CL, and the concentration of the polymer solutions. The unique phase transition behavior with temperature was observed by modified F68 triblock copolymer, composed of the PPO blocks core and the PEO blocks shell in aqueous solution. This phenomenon was elucidated using 1H NMR data; the alteration of hydrophobic interaction and chain mobility led to the formation of transparent gel, coexistence of gel–sol, and opaque gel. These hydrogels may be useful in drug delivery and tissue engineering.